Murray McCully has warned North Korea before: Stop playing with nukes. His condemnation of North Korea's latest nuclear test is unlikely to shake the young despot Kim Jong Un. But it's hard to see what will.

OPINION:
North Korea is a police state run by a bizarre despot. If it develops usable nuclear weapons, Armageddon becomes possible. Kim Jong Un seems to face none of the usual political constraints on madness. His people starve while he builds rockets. They rot in the gulag while he builds pyramids.

He seems, at least at first sight, free to grind his people without fear of revolution. Escapers from his state say there are murmurings about the cost of his nuclear project, but they are muted. Kim's murderers are everywhere and the people are terrified.

Nor does North Korea seem open to the usual kinds of diplomatic pressure. There have been false dawns before. Winston Peters, when he was foreign minister under the Helen Clark government, made a useful visit to North Korea as a messenger of the West.

At that time there were hopeful signs of a thaw in the Stalinist state. Negotiations over nukes were looking hopeful. Western negotiators said this to the New Zealand delegation while it was in Pyongyang. Mr Peters passed all this on to his good friend Condoleezza Rice, flying straight to meet her after leaving North Korea.

It all came to nothing. The notion that Western food aid could somehow bring North Korea to its senses over nuclear weapons seems to be forlorn. It might have some purchase if the despots were rational or affected by normal human feelings of shame or pity. But they are not.

The best hope, it seems, lies with China. It is North Korea's patron, neighbour and friend in a world that treats North Korea with loathing and contempt. Only China seems likely to shift its demented client. So far, it has failed to do so.

China is not, of course, the only big power to shore up dictatorships. For decades the United States did the same. "They're swine," went the argument, "but they're our swine." In recent times America has tended to turn away from this argument. Ms Rice spoke publicly about the flaws and fallacies on which it was based.

Breeding a stable of tame dictatorships is risky and likely to prove counterproductive. Dictators can fall very suddenly and unexpectedly; the Arab Spring is merely the latest proof of the danger. And then the people who suffered under the dictator are likely to loathe the Western states that propped him up (they are usually blokes.)

China is itself an undemocratic state, but it knows that sooner or later the Kim dynasty might fall. Even the most brutal tyranny is at risk from its own contradictions. Even the nastiest despot might fall victim to a palace coup – and a revolt at the top can spark a much wider insurrection.

Far better, then, for China to distance itself from the rogue state and pressure it to stop developing a nuclear missile that could be dropped on a civilised country. The world's safety might depend on it.